HVOF (High Velocity Oxygen fuel) refers to a process of thermal spray coating used to restore components surface properties, thus increasing its resistance to wear, erosion and corrosion. In this process, molten or semi molten material is exposed to high temperatures and high velocity gas stream to produce a dense spray coating that gives surfaces a quality finish.
HVOF coating can be used to apply different coating materials such as metals, ceramics, alloys and plastics to produce exceptional and outstanding adhesion to any substrate materials.
Unlike conventional plating process, the technique can be used to produce a wide range of products. It is safe and reduces the impact on the environment. The coating materials that can be used in thermal spray technique are: ceramics, alloys, metals, plastics and composites. Just like any other thermal spray coating procedures, HVOF coating materials can be heated and a gas stream used to give better results. The gas stream used in this process may be produced by mixing fuel and oxygen. This can be done in a combustion chamber where pressure builds up. A powder is them introduced into the stream where it is heated and accelerated towards the surface resulting into a thermal spray coating.
Advantages of HVOF Spraying
• Lower porosity because of the greater particle impact velocities
• It increases wear resistance because the coating is tougher and harder
• There is less degradation of carbide phases meaning that the hardness levels are higher.
• Lower oxide content as a result of less in-flight exposure time
• The powder chemistry is retained
• One can achieve thicker coating due to residual stresses.
• The surfaces sprayed are smooth due to high impact velocities and the reduced powder sizes
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• It is a complex process that depends upon numerous processes and variables.
• It requires experienced and qualified personnel to ensure that the operation is safe.
• There are numerous safety issues that must be addressed in the process.